As described in JP 2014-175365A, a waterproof construction is implemented with a vehicle-mounted case or the like that contains electric equipment to prevent a breakdown of the electric equipment, which is contained in the vehicle-mounted case, due to water infiltration. As in JP 2014-175365A, measures to seal the inside of a case with a sealing member result in an increased cost of manufacturing.
Accordingly, one of the objects is to provide a substrate unit that can reduce the adherence of water droplets to an internal circuit board with a simple construction.